The Marine Corps is set to have its first female infantry officer, a milestone in its nearly 250-year-long history.

The lieutenant is scheduled to graduate with her all-male peers on Monday after she completed all of the graduation requirements in the service's grueling 13-week Infantry Officer Course, the Corps said.

Her completion of the course was first reported by The Washington Post. The officer's name was not made public.

The course was opened to women in 2012, and on an experimental basis. More than 30 women attempted it, but when none passed, the course was once again closed to females in the spring of 2015.

After the Pentagon opened all military jobs to women, four additional women tried the course without success.

Meant to simulate infantry combat, the course pits students with loads of more than 150 pounds on their backs against stressful environments and grueling obstacle courses.

With its tests of strength, leadership and character, the course is seen as one of the most difficult in the military. About a quarter of those who attempt it wash out and end up in different areas of the military, according to the Post.

Monday's graduation will take place aboard Marine Corps Base Quantico in Virginia, service officials said.

Two sources told the Post that it's unlikely the lieutenant will come forward, preferring to be a "quiet professional" who focuses on her job.

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